Organosilicon compounds such as amine functional silicones have a wide utility in uses that include, but are not limited to, use in releasing agents, surfactants, copolymers in urethane or epoxy composites, polycarbonates and polyamides. Amine functional silicones also find utility in corrosion resistant coatings and polishes. Present commercial methods for manufacture of these materials suffer from several disadvantages.
Typical manufacture of amine functional silicones involves the reaction of allylamine and silicon-hydrogen functional silanes (or siloxanes) to prepare 3-aminopropyl functional silanes (or siloxanes). These components are coupled by a catalyzed hydrosilation reaction proceeding in the presence of materials such as platinum, rhodium, or other rare earth catalysts. In many cases, prior to the hydrosilation process, the allyl amine nitrogen-hydrogen bonds are partially or completely protected by blocking with trimethylsilyl groups. Upon completion of the hydrosilation step, the material is subjected to a de-blocking step to restore nitrogen-hydrogen bonds.
Many applications call for the use of specific organosilane isomers having the 3-aminopropyl functionality. In certain circumstances, it is the gamma isomer that is desirable, while materials such as the beta isomer are not. In circumstances where the ratio of desirable gamma-aminopropyl to undesirable beta-amino propyl substitution is reported, there is significant beta-isomer present. The presence of beta-isomer can be particularly undesirable in the production of siloxane-modified materials requiring heat stability such as siloxane-modified polyimides.
The respective boiling points for the beta and gamma isomers are quite close. Thus the removal of the beta-isomers of amine alkyl functional monomers (silanes) and disiloxanes has been accomplished through difficult separations by distillation, using complex, multi-plate distillation columns, owing to the very minor difference in boiling points between beta and gamma isomers of aminopropyl adducts. Additionally, the reaction of allyl amine with silicon-hydrogen containing components has been found to produce an impurity resulting from reaction of the amino end group with silicon-hydrogen to yieldSi—NH—CH2CH═CH2 again impacting the conversion to desired product.
The above considerations have been discussed in U.S. Pat. No. 5,892,084, which states that “[a] simple high-yielding process for producing 3-aminopropylsiloxanes, substantially free of isomeric 2-aminopropylsiloxanes, has clearly been sought for years, to no avail.” Further, U.S. Pat. No. 6,087,520 states that “Where is a need to have a method for preparing 1,3-bis(3-aminopropyl)tetramethyl disiloxane of quality in a commercially advantageous manner.”
The importance of an improved process for producing 3-aminopropyl functional silanes or siloxanes such as 3-aminoalkyl end blocked siloxanes and 3-aminoalkyl functional silanes can also be appreciated from the discussion in U.S. Pat. No. 5,026,890 where it is observed that “Commercial utilization of these compounds has been inhibited by the lack of convenient methods for their preparation on a large scale.”
Thus it would be desirable to provide a method for producing 3-amino-functional silanes and siloxanes such as 3-aminoalkyl end blocked siloxanes and 3-aminoalkyl functional silanes. It would also be desirable to provide a material that is essentially free of isomeric 2 aminopropylsiloxane components.